A procedure that is well-known has been used in the past for making ceramic shapes, namely mixing a binder and a gelling agent with a refractory and allowing the mix to chemically set or gel to form a bond and then firing the body. Typically many shapes have been made using sodium silicate, potassium silicate, colloidal silica, and hydrolyzed ethyl silicate as bonds. However, to obtain the greatest refractoriness of a body, a bond leaving a residue of a more refractory oxide is preferable. For example, alumina and zirconia produce high temperature bonds for refractories.
U.S. Pat. No. 4,025,350 shows the use of an aqueous solution of a zirconium salt with a gelling inducing agent and a gelling delaying agent and a refractory powder to form a refractory article. This composition requires additional gelling agents for control thereby increasing costs and control problems. Also the by-products of the gelation of the zirconium salt would need to be eliminated from the refractory during firing. There is also an added cost of the zirconium salt versus the oxide.
U.S. Pat. No. 4,201,594 describes the binding of refractory materials using zirconium salts and incorporating gelling agents and gel delaying agents. For the same reasons these compositions are less than desirable.
U.S. Pat. No. 2,984,576 describes an unfired mixture of a refractory material bonded with a zirconia or hafnia sol in which the percent of solids in the dispersed phase is at least 30%. This patent does not describe the specific refractories useful with the present stable acidic zirconia sol but only as a bond for a variety of refractories.
U.S. Pat. No. 3,758,316 describes the process for producing a refractory from a refractory powder and a binder precursor which would include colloidal zirconia, but also requires the addition of a gelling agent.